Fast quench reactor and method

A fast quench plasma reactor for thermal conversion of one or more reactants in a thermodynamically stable high temperature gaseous stream to a desired end product in the form of a gas or ultrafine solid particles, comprising:

• an enclosed reactor chamber arranged along a reactor axis, the reactor chamber having axially spaced inlet and outlet ends;
• a plasma torch including at least one pair of electrodes positioned at the inlet end of the reactor chamber;
• a plasma arc gas inlet upstream from the electrodes for introducing a stream of plasma arc gas between the electrodes at a selected plasma gas flow while the electrodes are subjected to a selected plasma input power level to produce a plasma within the reactor chamber and extending toward the outlet end of the reactor chamber, the plasma containing at least one reactant, whereby an incoming reactant stream is mixed into the plasma to progressively effect heat transfer between the plasma and a resulting gaseous stream as the gaseous stream flows axially toward the outlet end of the reactor chamber;
• at least one reactant inlet leading into the reactor chamber at or adjacent to its inlet end at a selected injection angle;
• the reactor chamber having a predetermined length sufficient to effect heating of the gaseous stream by the plasma to a selected equilibrium temperature at which a desired end product is available as a thermodynamically unstable reaction product at a location adjacent the outlet end of the reactor chamber;
• a coaxial convergent-divergent nozzle positioned in the outlet end of the reactor chamber for rapidly cooling the gaseous stream by converting thermal energy to kinetic energy as a result of adiabatic and isentropic expansion as it flows axially through the nozzle, the nozzle having a converging section and a diverging section respectively leading to and from a restrictive open throat;
• the converging section of the nozzle having a high aspect ratio for accelerating the gaseous stream rapidly into the nozzle throat while maintaining laminar flow;
• the size of the restrictive open throat within the nozzle being selected to control the residence time and reaction pressure of the resulting gaseous stream in the reactor chamber;
• the gaseous stream being accelerated to sonic velocities during passage through the throat of the nozzle to transform thermal energy of the moving gaseous stream into kinetic energy in the axial direction of gas flow, thereby retaining the desired end product within the flowing gaseous stream;
• the diverging section of the nozzle then subjecting the gaseous stream to an ultra fast decrease in pressure by smoothly accelerating and expanding the moving gaseous stream;
• a coaxial cool down chamber leading from the diverging section of the nozzle for reducing the velocity of the moving gaseous stream while removing heat energy at a rate sufficient to prevent increases in its kinetic temperature to retain the desired end product within the gaseous stream;
• and wherein the diverging section of the nozzle and cool down chamber are designed to minimize undesired side or back reactions;
• and
• a product collector downstream of the cool down chamber to separate a desired reaction product from the gases exiting the cool down chamber.

A method for thermally converting one or more reactants in a thermodynamically stable high temperature gaseous stream to a desired end product in the form of a gas or ultrafine solid particles, comprising the following steps:

• introducing a reactant stream at one axial end of a reaction chamber;
• rapidly heating the incoming reactant stream as the reactant stream flows axially toward the remaining end of the reactor chamber;
• the reactor chamber having a predetermined length sufficient to effect heating of the gaseous stream to a selected reaction temperature at which a desired end product is available as a thermodynamically unstable reaction product at a location adjacent the outlet end of the reactor chamber;
• passing the gaseous stream through a restrictive convergent-divergent nozzle arranged coaxially within the remaining end of the reactor chamber to rapidly cool the gaseous stream by converting thermal energy to kinetic energy as a result of adiabatic and isentropic expansion as it flows axially through the nozzle and minimizing back reactions, thereby retaining the desired end product within the flowing gaseous stream;
• and
• subsequently cooling and slowing the velocity of the desired end product and remaining gaseous stream exiting from the nozzle.

A method for thermal conversion of one or more reactants in a thermodynamically stable high temperature gaseous stream to a desired end product in the form of a gas or ultrafine solid particles, comprising the following steps:

• introducing a stream of plasma arc gas between the electrodes of a plasma torch including at least one pair of electrodes positioned at the inlet end of an axial reactor chamber, the stream of plasma arc gas being introduced at a selected plasma gas flow while the electrodes are subjected to a selected plasma input power level to produce a plasma within the reactor chamber and extending toward its outlet end;
• thoroughly mixing an incoming reactant stream into the plasma by injecting at least one reactant into the reactor chamber at or adjacent to its inlet end at a selected injection angle and at a selected reactant input rate to progressively effect heat transfer between the plasma and the resulting gaseous stream as it flows axially toward the outlet end of the reactor chamber;
• the length of the reactor chamber being sufficient to effect heating of the gaseous stream to a selected equilibrium temperature at which a desired end product is available as a thermodynamically unstable reaction product within the gaseous stream at a location adjacent to the outlet end of the reactor chamber;
• directing the gaseous stream through a coaxial convergent-divergent nozzle positioned in the outlet end of the reactor chamber to rapidly cool the gaseous stream by converting thermal energy to kinetic energy as a result of adiabatic and isentropic expansion as it flows axially through the nozzle, the nozzle having a converging section and a diverging section respectively leading to and from a restrictive open throat;
• cooling the gaseous stream exiting the nozzle by reducing its velocity while removing heat energy at a rate sufficient to prevent increases in its kinetic temperature;
• and
• separating desired end products from the gases remaining in the cooled gaseous stream.

A method for producing titanium, comprising the following steps:

• decomposing a titanium compound by introducing it as a stream of vapor into a hot plasma together with one or more reactants;
• directing the resultant hot gaseous stream through a convergent-divergent nozzle to allow its contents to reach thermodynamic equilibrium prior to being subjected to an ultrafast decrease in pressure;
• and
• quenching the titanium within the hot gaseous stream by introducing cold gas into it as it passes through the nozzle to cool its contents at a rate that condenses titanium and inhibits formation of equilibrium products as the resulting gaseous stream exits the convergent-divergent nozzle.